Spurious messages for functions as instance attributes

[inducer]

Bug Report

Run this code:

from typing import Callable
from dataclasses import dataclass


@dataclass(frozen=True)
class Face:
    map_to_volume: Callable[[int], int]

f = Face(map_to_volume=lambda x: x)

f.map_to_volume(5)

through mypy 0.920 on Python 3.10 and get the following output:

$ mypy mypy-bug.py
mypy-bug.py:12: error: Invalid self argument "Face" to attribute function "map_to_volume" with type "Callable[[int], int]"
mypy-bug.py:12: error: "int" not callable
Found 2 errors in 1 file (checked 1 source file)

Expected Behavior

• I'm surprised to see mypy complain about a self argument for map_to_volume. It's an instance attribute, not a class attribute, so it is not subject to method processing. Python seems to agree, no self argument is passed.
• The message about int not being callable seems spurious: f.map_to_volume is not an int.

Your Environment

• Mypy version used: 0.920
• Mypy command-line flags: (none, see above)
• Mypy configuration options from mypy.ini (and other config files): (none)
• Python version used: 3.10
• Operating system and version: Linux, Debian testing/unstable

x-ref: inducer/modepy#45, which tries to remove a type: ignore that was necessitated by #9975.

[hauntsaninja]

Thanks, duplicate of #5485

See also #11571 and #10548